1. Field of the Invention
The present invention relates to a connection socket structure for a light source device used for endoscopes through which light guide means of an endoscope is connected to the light source device to transmit light from the light source to the endoscope.
2. Description of Related Art
Typically, during the use of an endoscope, light is conducted to the endoscope from a light source through light guide means such as an optical fiber or an optical fiber bundle and sent out from an exit aperture at a distal end of the endoscope for a medical illumination purpose such as for illumination of the interior of a body cavity. The light guide means of the endoscope is connected to a light source device through a connection socket installed to the light source device. As seen in FIG. 7 showing a conventional light source device 100 by way of example, the light source device 100 includes a high intensity light source lamp 30 such as a metal halide or xenon arc lamp and an optical system 31 in axially alignment with each other in a light source housing 32. The optical lens system 31 collects and condenses light from the light source lamp 30. The light source device 100 is provided with a connection socket 101 through which light guide means 20 of an endoscope (not shown) is detachably connected to the light source device 100. The light guide means 20 includes a fiber bundle 21 with a distal end portion typically encased within a cylindrical connection ferrule and a coupling cap 23. For mechanical connection of the distal end of the light guide means 20, the coupling cap 23 is screwed, or otherwise bayonet-coupled, to the connection socket 101. Light from the light source lamp 30 in the light source device 100 is conducted to the endoscope through the light guide means 20. If the distal end of the light guide means 20 is too small in outer diameter to fit snugly into a slot or aperture of the connection socket 101 without backlash, the fiber bundle 21 of the light guide means 20 is misaligned in optical axis with the light source lamp 30, so as to cause a quantitative deficiency of light to be conducted to the endoscope through the light guide means 20. The quantitative deficiency of light leads directly to a deterioration of illumination for a body cavity. In these circumstances, the distal end of the optical fiber bundle or the single optical fiber is generally encased within a cylindrical connection ferrule for insertion into a slot or aperture within the connection socket 101 of the light source device 100. The cylindrical connection ferrule has a three-dimensional profile matching the interior profile of the aperture of the connection socket 101 so as to ensure that the cylindrical connection ferrule remains snugly mounted within the aperture of the connection socket 101 without rattling. The provision of the removable connection ferrule allows a single light source device to be used to provide light for a variety of endoscopes, each having a corresponding connection ferrule.
However, problems arise in many conventional endoscopes, particularly those having different cylindrical ferules. In order to allow a single light source device for various endoscopes provided with cylindrical connection ferrules having different three-dimensional profiles, respectively, one of the conventional light source devices is provided with a plurality of connection sockets which have apertures different in interior profile one another but matching different three-dimensional profiles of the cylindrical connection ferrules respectively, or alternatively with a single connection socket having a slot or aperture variable in interior profile correspondingly to the different three-dimensional profiles of the cylindrical ferules. Examples of these conventional light source devices are disclosed in, for example, Japanese Unexamined Patent Publication Nos. 2-50447, 11-183808 and 2001-125010.
Reference is made to FIGS. 8A, 8B and 9 for the purpose of providing an understanding of a connecting configuration of light guide means of endoscopes having cylindrical connection ferrules different in outer diameter from one another to a light source device 100 such as shown in FIG. 7 through a connection socket installed to the light source device 100.
FIGS. 8A and 8B show one example of a connection socket 101 of a conventional light source device 100 (see FIG. 7) adapted for use with various endoscopes having different light guide means 20a and 20b, respectively. For example, one of the endoscopes shown in FIG. 8A has thin light guide means 20a including a fiber bundle 21a with a distal end portion encased within a cylindrical connection ferrule 22a and the other shown in FIG. 8B has thick light guide means 20b including a fiber bundle 21b with a distal end portion encased within a cylindrical connection ferrule 22b which is, for example in this example, greater in outer diameter than the cylindrical connection ferrule 22a of the thick light guide means 20a. The connection socket 101 comprises a connection socket housing 104 having a connection lip 104a and fixedly installed to the light source device 100, a positioning block 102 slidably received within the connection socket housing 104 and biasing means 103 such as a coil spring disposed between the positioning block 102 and the connection socket housing 104. The positioning block 102 has a tapering cone-shaped aperture 102a with a truncated end opening 102b formed therein and is urged toward the connection lip 104a by the biasing means 103. When connecting the thin light guide means 20a or 20b to the light source device 100, the distal end portion of the light guide means 20a or 20b is inserted into the tapering cone-shaped aperture 102a until the cylindrical connection ferrule 22a or 22b is brought into abutment with inner surface of the tapering cone-shaped aperture 102a and then the coupling cap such as shown in FIG. 7 is screwed to the connection lip 104a of the connection socket housing 104 of the connection socket 101. During screwing the connection cap, the connection ferrule 22a or 22b forces the positioning block 102 toward the optical lens system 31 the against the biasing means 103. When the connection cap is fully screwed to a given position with respect to the connection socket 101, the light guide means 20a or 20b is firmly connected to the light source device 100 and aligned with an optical axis Lx of the optical lens element 31 by the connection socket 101 and. In the connected position, an entrance aperture of the light guide means 20a or 20b is put in a plane in conformity with a focal plane of the optical lens system 31, where light from the light source lamp 30 is most efficiently collected and condensed.
More specifically, as shown in FIG. 8A, when connecting the thin light guide means 20a having the cylindrical connection ferrule 22 to the light source device 100, the cylindrical connection ferrule 22a is inserted into the tapering cone-shaped aperture 102 of the positioning block 102 until it is brought into abutment with the inner surface of the positioning block 102. Further, when the coupling cap is fully screwed to the connection lip 104a of the connection socket 101, the positioning block 102 is forced against the biasing means 103 and placed at a distance from the optical lens system 31 so as thereby to position the entrance end of the fiber bundle 21 encased within the cylindrical connection ferrule 22a of the thin light guide means 20a in the focal plane of the optical lens system 31. On the other hand, as shown in FIG. 8B, when connecting the thick light guide means 20b having the cylindrical connection ferrule 22b to the light source device 100, the cylindrical connection ferrule 22b is inserted into the tapering cone-shaped aperture 102 of the positioning block 102 until it is brought into abutment with the inner surface of the positioning block 102. Further, when the coupling cap is fully screwed to the connection lip 104a of the connection socket 101, the positioning block 102 is forced against the biasing means 103 and placed at a distance from the optical lens system 31, shorter than the distance in the case where the thick light guide means 20b having the cylindrical connection ferrule 22b larger in diameter than the cylindrical connection ferrule 22a of the thin light guide means 20a, so as thereby to position the entrance end of the fiber bundle 21b encased within the cylindrical connection ferrule 22b of the thick light guide means 20b in the focal plane of the optical lens system 31.
The provision of the tapering cone-shaped aperture 102a in the positioning block 102 allows the single light source device 100 to be commonly used to a variety of endoscopes which have different light guide means with distal end portions encased within cylindrical connection ferrules, respectively, different in outer diameter from one another.
FIG. 9 shows another example of a connection socket 101 of the conventional light source device 100 (see FIG. 7) adapted for use with various endoscopes. The connection socket 101 includes retainer means comprising a plurality of, for example three in this example, retainer units 105 arranged at regular angular intervals, namely 120°, in a plane perpendicular to an optical axis Lx of the optical lens system 31 (see FIG. 7). Each of the retainer units 105 comprises a generally square-shaped retainer plate 106 pivoted on a spring-loaded pivot shaft 107 at one corner thereof and a biasing means 108 such as a compression spring fixedly mounted to another corner of the square-shaped retainer plate 106 adjacent to the one corner. The spring-loaded pivot shafts 107, that are secured to a connection socket housing similar to that of FIGS. 8A and 8B, are arranged at regular angular intervals, namely 120°, on a circle having a center on the optical axis Lx of the optical lens system 31 in a plane perpendicular to the optical axis Lx of the optical lens system 31 and bias the square-shaped retainer plates 106 to pivotally turn in a counterclockwise direction in FIG. 9. The three biasing means 107 form an aperture for insertion of cylindrical connection ferrules into the connection socket among them and provide biasing force oriented toward the optical axis Lx of the optical lens system 31.
The pivoted retainer units 105a, 105b and 105c of the connection socket are pivotally turned in a clockwise direction about the spring-loaded pivot shafts 107, respectively, according to a diameter of cylindrical connection ferrule 22×of image guide means of an endoscopes and snugly hold them by the biasing means 108. The connection socket including the pivoted retainer units 105a, 105b and 105c allows light guide means of having cylindrical connection ferrules 22×different in diameter of various endoscopes to be connected to the single light source device.
However, problems arise in these conventional light source devices 100, particularly those provided with a plurality of connection sockets having different apertures matching different profiles of connection ferrules of light guide means of various endoscopes, it is hard to position entrance apertures of the different light guide means in a desired position, for example a focal plane of the optical lens system 31 wherein light from the light source lamp 30 is most efficiently collected and condensed. Alternatively, if the light source device 100 is designed to shift the light source lamp 30 in position according to respective light guide means, the light source device 100 is undesirably made bulky for securing a large space for the light source lamp 30.
Regarding the light source device 100 provided with the connection socket 101 including the positioning block 102 having a tapering cone-shaped aperture 102a for use with various endoscopes having light guide means different in diameter of their connection ferrules from one another, a light beam from the light source lamp 30 through the optical lens system 31 is partly blocked by the truncated end opening 102b of the tapering cone-shaped aperture 102a of the positioning block 102. In consequence, it is hard to direct light always most efficiently onto entrance apertures of the different light guide means.
Further, regarding the light source device 100 provided with the connection socket 101 including a plurality of, for example three pivoted retainer units 105a, 105b and 105c for use with various endoscopes having light guide means different in ferrule diameter from one another which provide biasing force toward the optical axis Lx of the optical lens system 31 in a plane perpendicular to the optical axis Lx of the optical lens system 31, force that is provided by the connection socket 101 and countervails against force applied to the light guide means in a direction perpendicular to a direction of insertion of the light guide means is too weak to hold the light guide means in axial alignment with the light source lamp 30 during use of the endoscope. If employing the pivoted retainer units 105a, 105b and 105c designed to provide sufficiently strong force for holding the light guide means, the biasing means 108 has to provide strong spring force or has to have high resilient force and, in consequence, is inescapably large in size.